Population structure of Bartonella henselae in Algerian urban stray cats

Abstract

Whole blood samples from 211 stray cats from Algiers, Algeria, were cultured to detect the presence of Bartonella species and to evaluate the genetic diversity of B. henselae strains by multiple locus VNTR analysis (MLVA). Bartonella henselae was the only species isolated from 36 (17%) of 211 cats. B. henselae genotype I was the predominant genotype (64%). MLVA typing of 259 strains from 30 bacteremic cats revealed 52 different profiles as compared to only 3 profiles using MLST. Of these 52 profiles, 48 (92.3%) were identified for the first time. One-third of the cats harbored one MLVA profile only. As there was a correlation between the age of cats and the number of MLVA profiles, we hypothesized that the single profile in these cats was the profile of the initial infecting strain. Two-third of the cats harbored 2 to 6 MLVA profiles simultaneously. The similarity of MLVA profiles obtained from the same cat, neighbor-joining clustering and structure-neighbor clustering indicate that such a diversity likely results from two different mechanisms occurring either independently or simultaneously: independent infections and genetic drift from a primary strain.

Figure 1. Association between the proportion of bacteremic cats and the age of cats.

Figure 2. Polymorphism of BHV-A in 10 B. henselae strains by agarose gel electrophoresis.

Lanes number 1 to 10: B. henselae strains isolated from cat # 92.

Figure 3. Minimum Spanning Tree of 52 B. henselae strains from Algiers and 114 strains from other part of the World on categorical analysis of 5 VNTRs.

Each circle represents a unique genotype. The diameter of each circle corresponds to the number of strains with the same genotype. Genotypes connected by a shaded background differ by a maximum of 1 of the 5 VNTR markers. Thick connecting lines represent one marker difference; regular connecting lines represent two marker differences; thick interrupted lines represent three differences. The length of each branch is also proportional to the number of differences. Each geographical situation is represented by a specific colour: red for strains collected in Asia, yellow for strains collected in Europe, green for strains collected in North-America, purple for strains collected in Australia and blue for strains collected in North-Africa.

Figure 4. Distribution average distance between profiles of strains isolated from the same cat.

Observed average distance between MLVA profiles obtained from the same cat (star) and distribution of simulated values under the null hypothesis that two pairs of MVLA profiles obtained from the same cat are as similar as two pairs of MVLA profiles obtained from different cats.

Figure 5. Dendrogram of the profiles generated by Neighbor Joining.

Each profile is identified by: [Number of Cat(s)] VNTR profile (16SrRNA genotype). Frames identify B. henselae 16S rRNA type II.

Figure 6. Structure-neighbor clustering analysis of MLVA profiles.

Two clusters are defined. Within each cluster, each profile is connected to its nearest neighbor(s) and the corresponding distance is indicated (the mean difference between the number of repeats). Each profile is identified by: [Number of Cat(s)]/VNTR profile/(16SrRNA genotype).